We are using Exchange 2010 on SBS2011 and additionally Eset Mail Security. We receive just a huge amount of spam in to our mailboxes. I have tried to configure Eset to prevent that, but everything is just not right enough. For example greylisting - it should work against spam, however, even if whitelist is configured - it still prevents most of emails to come through without a delay. Is there anything else, where greylisting looks up for whitelists? Or where shall we consider configuring whitelists if not in Eset?

I've been working with whitelisting for a a short time now. What are you using for whitelisting - is it "aproved senders" ?
Note that I found a problem with greylisting - namely that there seems to be a lot of sending servers which do not retry the messages.

Yes, these senders are approved. Gmail, yahoo, hotmail - the basic ones. As well as, few more domains as 1and1.co.uk etc.

My manager said, we had less spam in past time with Eset. For some time we had to manage our networks without Eset protection and recently we installed it back. Since then, I am trying to set it up against all the spam, however, I can't see many options for that. Greylisting is the only one feature, which I found as the most reasonable. It delays common domains, not for a long time - about 20-40 mins (setup is set for 7 hours), but it is still inconvenient.